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Evidence of Evolution

Picture of Charles Darwin
Click on image for full size The Bettmann Archive

The Theory of Natural Selection

During the 19th century when Europeans were exploring their own countries as well
as mounting large expeditions to explore foreign lands, natural historians such
as Charles Darwin and Alfred Russel
Wallace were making observations of the geographic distributions of species. They
found that different species were found in different environments. Species in the
tropics were well suited, or adapted, to live in the tropics and species in England
were well adapted to live in England. Finches on different Galapagos Islands were
well adapted to their particular environments. Independent of one another, Darwin and Wallace
both developed the theory of natural selection to explain
the geographic distributions of species. That theory states that there are variations
in organisms of the same species. Some are tall, some are short, some have larger
mouths, keen eyesight, etc. The organisms that are most well suited to live in
a particular environment are more likely to survive. The survivors produce the next generation and those offspring are more likely to have their parent's special traits (such as keen eyesight, etc.)

Here are the main points of the theory of natural selection:

Everyone’s Different: There are variations among individuals of the
same species (better eyesight, extra feathers, longer legs, etc.)

Resources are Limited: Resources such as food and shelter are limited

Lots of Babies: Organisms make more babies (young) than could actually live in the environment.

Organisms Compete: Organisms compete for food and other resources in the
environment.

The "Fittest" Survive: The organisms whose variations best fit the
environment are most likely to survive, reproduce, and pass useful traits
to the next generation.

The evidence of evolutionary changes in life forms through time has been well
established and accepted for more than a century. Natural selection is an explanation
for the mechanism of evolution. In addition, scientists continue
to investigate more specific hypotheses that might further develop our understanding of how change through
time happens. One of the main hypotheses, developed by Stephen
J. Gould and Niles Eldridge, is called punctuated equilibrium. This hypothesis suggests that
the rate of change in a population is not constant. No changes, or very few, may happen to a population of
organisms over millions of years and then changes may happen rapidly over many thousands
of years. Advances in technology over the past century have allowed scientists
to continue to test hypotheses that further our understanding of evolutionary
processes.

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